Japanese Patent Application Laid-Open Publication No. 07-291150 (JP 07-291150 A) discloses a vehicle body in which various reinforcements are implemented in order to increase the rigidity of a floor panel or another such flat panel.
In the vehicle body structure disclosed in JP 07-291150 A, the floor panel is reinforced by a bead that is long and thin in the longitudinal direction of the vehicle body, a bead that is long and thin in the width direction of the vehicle, and a cross member that is long and thin in the width direction of the vehicle.
The bead (longitudinal bead) that is long and thin in the longitudinal direction of the vehicle body and the bead (transverse bead) that is long and thin in the width direction of the vehicle are formed so as to intersect with each other on the surface of the floor panel. The cross member is a member formed so as to be substantially U-shaped as seen from the side of the vehicle body, the cross member covers the top of the transverse bead, and the cross member is connected to the floor panel. As a result, the portion where the substantially U-shaped cross member and the floor panel are joined is formed into a closed cross section shape as seen from the side of the vehicle body.
However, in the vehicle body structure disclosed in JP 07-291150 A, the longitudinal bead is blocked by the transverse bead. Moreover, the cross member is connected to the floor panel alone, and is not connected to the longitudinal bead or the transverse bead. Therefore, there is a limit on how much of an increase can be achieved by means of the longitudinal bead, the transverse bead, and the cross member in the rigidity of the floor panel in the portions where the beads intersect with each other.
In the vehicle body structure disclosed in JP 07-291150 A, depending on the vehicle, there are cases in which various pipes pass through the inner sides of the longitudinal bead. In this case, the longitudinal bead must have a height sufficient to allow pipes to pass through, even in the portion that intersects with the cross member and the transverse bead. Therefore, the cross member and the transverse bead have portions cut out where the longitudinal bead passes through. Consequently, there is room for improvement in ensuring rigidity in the cross member and the transverse bead.
A possibility that has been considered is to divert portions upward in the cross member where the longitudinal bead passes through. However, the height of the cross member would increase in the diverted portions. Since the passenger compartment must be accommodating, there is a limit on how much the height from the floor panel to the top surface of the cross member can be increased. Moreover, it is inadvisable because the weight of the vehicle body increases proportionate to the diverted portions.
In view of this, there is a demand for a technique whereby it is possible to increase the rigidity of the portions where reinforcing members intersect with each other, as well as the rigidity of the floor panel in the intersecting portions.